Think of the world’s smallest diamonds.
Now divide that by about a billion, because we aren’t talking an engagement ring here.
These are diamondoids, the smallest possible diamond crystals.
Adamantane, a carbon-cage molecule and the smallest diamondoid, has just 10 carbon atoms and 16 hydrogen atoms.
It’s less than a billionth of a billionth of a carat.
What does that have to do with the petroleum industry?
Diamondoids occur naturally in crude oil and gas liquids – first identified and isolated from Czechoslovakian crude in 1933.
Skip ahead a few decades. Today, nanotechnology researchers are studying diamondoids for all sorts of potential uses.
Current research into diamondoids is “going in every direction.
“Basically, every field is involved with nanotechnology,” said Nick Melosh, assistant professor in the Department of Materials Science and Engineering at Stanford University in Stanford, Calif.
Melosh is working with a research grant from Chevron Corp. to study the nature of diamondoids, with an eye toward practical applications of nanotech.
And his research truly occurs at nano-scale. He said each individual diamondoid measures about one nanometer by half a nanometer.
“There aren’t huge ones, yet – the largest ones isolated are six diamond cages long, about 1.3 nanometers,” Melosh said. “People are still trying to figure out how to process these things.
“Only in the last year and a half have modified versions of diamondoids become available that are much easier to handle. ”
Excellent Emitters
Right now, Melosh and his research students spend time studying the unique properties of diamondoids.
Like most nano-scale materials, diamondoids sometimes behave differently from their large-scale counterparts, and sometimes similarly.
“They’re like diamonds in some ways, so they’re probably very mechanically and electronically stable,” Melosh said. “And they are very robust in our experiments, especially mechanically.”
As it turns out, diamondoids make excellent field emitters – they are very good at emitting electrons “for various unknown reasons,” he noted.
Melosh has studied that capability with ultraviolet spectroscopy, using UV light to excite electrons off the diamondoids’ surface.
“In this case, we had these diamondoids self-assembled on a layer of gold or silver, ” he said.
They emitted all electrons at the same energy level in those experiments, acting as tiny but efficient producers. That could point toward uses in improved solar cells, nano-batteries and low-energy lighting, according to Melosh.
“You can get very high efficiencies of current-in to current-out,” he observed.
Because of their efficiency, diamondoids could be coming to your TV screen, if field emission devices (FEDs) replace liquid-crystal display (LCD) technology.
FEDs may offer sharper images while using less power than today’s displays.
In October, researchers reported the results of new diamondoid experiments at the Advanced Light Source (ALS) division of the Lawrence Berkeley National Laboratory.
They found that 68 percent of all emitted electrons from a diamondoid monolayer on silver were within a single energy peak, said Wanli Yang, a physicist at the ALS lab.
“This monochromatic emission is several times stronger than that reported for bulk diamond surfaces, which means much more electrons were emitted at the same speed, a very desirable property for use in FEDs, ” Yang noted.
The Human Element
But diamondoids’ most important benefits for human beings should come inside human beings.
“The biggest thing you see coming up in nano right now is biology,” Melosh said.
“We’re actually looking at how to get conventional semiconductor technology interfaced with biological constructs, like cells, ” he explained.
That research partly involves the potential use of nano-scale patterns and chemical release to regulate cell behavior. For his studies, Melosh has used stem cells derived from fat, a much less controversial stem cell source.
“You can actually harvest a fair amount of these adipose stem cells from fat, and people don’t have the same level of objection to liposuction,” he said.
One challenge is how to stimulate or record nerve activity without degrading the nerves, Melosh said.
The payoff could be practical nanotech-biology interfaces – we’re talking Bionic Man now.
“It would be great for things like prosthetics,” he said. “The big question is, how do you interface nerves with these new kinds of prosthetics?”
Diamondoids burst into the news, sort of, when Chevron MolecularDiamond Technologies announced it had successfully identified, isolated and produced groups of higher-level diamondoids.
Adamantane is the simplest form of diamondoid, a basic cage structure of the diamond lattice. Diamantane has two face-fused cages, and triamantane is somewhat more complex. Those are usually known as lower diamondoids.
The researchers at the Berkeley Lab used tetramantane with four cages, or higher diamondoids.
Each level of naturally occurring, higher diamondoid becomes exponentially more scarce, according to Melosh.
“There’s very, very little pentamantane,” he observed.
And for the Oil Industry …
Chevron rocked the world three years ago when it first announced the availability of higher diamondoids in quantity.
Okay, maybe that story didn’t make it onto the front page of your newspaper. But it represented an important step forward for diamondoid research.
Now we think nothing of going to parties and discussing C26H30 hexamantane, known as cyclohexamantane in casual conversation, which also occurs naturally in petroleum.
The point? Higher diamondoids and diamondoids of different structures are now available to researchers in gram quantities, plenty enough for research work.
Current studies focus on electronics and biology, but it’s likely that diamondoids someday will find useful applications in oil and gas.
Then they’ll complete the cycle, providing benefits for the industry that gave them birth.